DC-to-DC converters are widely used to convert power from one form to another, such as to provide a desired voltage or impedance transformation. Examples of DC-to-DC converters include, but are not limited to, buck-type DC-to-DC converters, boost-type DC-to-DC converters, and buck-boost type DC-to-DC converters. Some DC-to-DC converters include multiple parallel-coupled power stages, or phases, such that the DC-to-DC converters may be referred to as multi-phase DC-to-DC converters. The power stages of multi-phase DC-to-DC converters are typically switched out-of-phase with respect to each other, to achieve ripple current cancelation, high effective switching frequency, and fast transient response.
DC-to-DC converters commonly regulate their output voltage by causing a magnitude of the output voltage to be substantially equal to a desired reference voltage. For example, FIG. 1 illustrates a prior art DC-to-DC converter 100 including an input port 102, an output port 104, a power stage 106, a controller 108, and an output capacitor 110. Power stage 106 is electrically coupled between input port 102 and output port 104, and output capacitor 110 is electrically coupled across output port 104. A comparison block 112 of controller 108 compares the magnitude of output voltage VOUT to a magnitude of a reference voltage VREF. Regulation control circuitry 114 controls power stage 106 such that the magnitude of output voltage VOUT is substantially equal to the magnitude of reference voltage VREF.
Some DC-to-DC converters include an unregulated operating mode where output voltage is unregulated. In this operating mode, the output voltage is allowed to fall or decay at a rate governed by discharge of output capacitance, until the output voltage reaches a target voltage. For example, in one embodiment of DC-to-DC converter 100 of FIG. 1, controller 108 shuts down power stage 106 in response to a command 116 to enter an unregulated operating mode, such that output voltage VOUT is allowed to fall until it reaches a target value. The rate at which output voltage VOUT falls during this unregulated operating mode is governed by discharge of output capacitor 110 and any other capacitance electrically coupled across output port 104.